From cppreference.com
constexprautocend(); (1) (since C++23)constexprautocend()constrequiresranges::range<constD>; (2) (since C++23)The default implementation of cend() member function returns the sentinel for the constant iterator of the range.
1) Let derived be a reference bound to static_cast<D&>(*this). Equivalent to returnranges::cend(derived);.
2) Same as (1), except that derived is static_cast<constD&>(*this).
Return value
The sentinel for the constant iterator of the range.
Notes
All range adaptors and range factories in the standard library and
use the default implementation of cend.
Example
See also
(C++11)(C++14)
returns an iterator to the end of a container or array
(function template)
(C++20)
returns a sentinel indicating the end of a read-only range
(customization point object)